Ancient Plant Protein Could Create Climate-Resilient Crops

At the end of what NASA says was the hottest global three-month period ever recorded, people in the Northern Hemisphere in particular are looking for some sort of relief. But, in truth, some 23 million years ago, our planet was much hotter than today.

So how did how did Earth’s ecosystem cope?

It turns out that it used a plant protein which still spans the globe. In its ancient form, Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), helped plants protect themselves from the heat. Trouble is, today, this ancient form of Rubisco is no longer available.

But an early career Cornell University researcher is working on a way to reconstruct this ancient Rubisco so that it can be reintegrated into food crops. The idea is to mitigate at least some of the deleterious effects that the current and projected future rise in temperatures is expected to have on agriculture.

To that end, the U.S. Dept. Of Energy has just awarded Cornell plant biologist Laura Gunn an $875,000 grant to explore this ancient enzyme, which is a key component of photosynthesis.

“The impetus for this work comes from the need to have climate-resilient crops, especially for food production,” Gunn told me via email. By replacing modern Rubiscos with their ancient, reconstructed counterparts, plants could perform photosynthesis more efficiently at higher temperatures, she says.

Global Temperatures Will Continue To Rise

Earth’s temperatures are projected to increase by five to six degrees Celsius by 2100, says Cornell. In contrast, Earth’s Miocene Epoch —- ranging from 23.5 to 5 million years ago —- had average global temperatures some eight degrees Celsius higher than today. This is thought to have been primarily due to various forms of global volcanism.

Although ancestral Rubiscos operated in a hot and high carbon dioxide-rich environment, they had time to adapt to that environment, says Gunn. And when the Earth slowly cooled, the Rubiscos adapted to that environment as well, causing them to lose their ability to perform better at higher temperatures.

But evolution takes time. And today’s Rubiscos have not had sufficient time to naturally re-adapt to rising global temperatures during the last 200 years of the industrial era.

Except for parasitic plants, all plants are dependent on Rubisco to produce carbohydrate precursors, says Gunn. Rubisco “fixes” CO2 into carbohydrates that organisms can use as a source of energy, she says. Every carbon atom in our bodies has at some point been “fixed” by a plant and incorporated into our bodies by either eating that plant, or an animal that ate that plant, says Gunn.

The Work Is Just Beginning

Gunn seeks to understand the basic biology of these ancient Rubiscos, find top performers, then create new Rubisco variants that could be grafted into modern plants, says Cornell.

The reconstructed Rubisco is not yet inside a plant, says Gunn. All our work is currently being performed by expressing it in e. Coli, a bacterium that we use as a tool to quickly manipulate and produce bucketloads of ancient Rubiscos for testing, she says.

As for transferring the reconstructed Rubisco into the target crop?

DNA encoding for the ancient Rubisco will be introduced to the plant through a process called chloroplast transformation, using a gene gun; often called biological ballistics, says Gunn. The DNA is coated with either gold or tungsten particles “shot” into plant tissue, she says. This metal-coated DNA is very literally fired at leaf tissue, says Gunn.

When Will We See Benefits?

This is not a quick fix; we are trying to implement lessons from millions of years of evolution within a single human lifetime, says Gunn. We will have proof of concept in tobacco plants within five years, she says. Then it will need to be translated to crops, which could take another five to ten years, says Gunn.

As for its ultimate use in mitigating climate change?

New Rubisco variants would have to be engineered into major crops like grains, potatoes, soybeans, sweet potatoes, and maybe even grasses and alfalfa intended for livestock feed, bioprocess engineer Jean Hunter, a Cornell University professor emeritus, told me via email.

There’s lots of work to prove that an engineered Rubisco can outperform a native Rubisco, Hunter told me. Researchers would have to make it work in a genetically wide range of commodity crops, she says.

Finally, as Hunter notes, these new modified crop seedstocks would need to be made accessible to farmers in under-resourced regions like Pakistan and Bangladesh.

They will need it more than our large corporate farmers in Nebraska, says Hunter.

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